Distillation apparatus for treating fatty acid containing stock



Oct. 5, 1948. v PQTTS 2,450,611

' DISTILLATION APPARATUS FOR TREATING FATTY ACID CONTAINING STOCK Original Filed Oct. 9, 1939 Patented Oct. 5, 1948 UNITED STAT-ES Ralph H.

of Illinois DISTILLATION APPARATUS FOR TREATING FATTY ACID CONTAINING STOCK Potts, La Grange. 1ll., mour and Company, Chicago, Ill.,

assig'nor to Ara corporation Continuation ofapplication Serial No. 424.434, I

December 26, 1941, wh cation Serial No. 298,72 application February 10,

11 Claims. (01. ace-154) This invention relates to treating fatty acidation of my ccpending application Serial No.

424,434, filed December 26, 1941, now abandoned, which is in turn a division of my copending application Serial No. 298,722, filed October 9, 1939, now matured. into Patent No. 2,322,056, issued June 15, 1943.

It is now common practice to pass fatty acidcont-aining stock through .a pipe still and thence into a fractionating tower, steam being employed inthe bottom of the tower for stripping the bottoms, the steam and the uncondensed portion of the stripped vapors passing up and out of the tower. This process has several disadvantages. The volume of the steam, air and other gases introduced with the feed stock makes it difficult to maintain the desired high vacuum. Furthermore, the ascending steam and gases, by reason of molecular weight differences and through entrainment, militate against sharp separation of the fractions. The presence of air and low boiling fractions tends to produce decomposition and discoloration. The non-uniform content of moisture within the feed stock produces an addi- I tional steam load in the fractionating tower and surging due to varying amounts of moisture.

An object of the present invention is to produce a sharp separation of the fractions within the fractionating tower through the "exclusion of steam and such gases, and, in general, to overcome the disadvantages above referred to. Afurther object is to improve yields, insure closer cut fractions of improved odor and color, prevent decomposition of the unsaturated fractions, and reduce operating costs. Another object is to provide apparatus in which the stock is first stripped or fractionated with steam and is thereafter distilled at a lower pressure. A further object is to provide apparatus in which the steam which is necessary for stripping the bottoms is substantial- 1y excluded from the fractionating tower, the same steam which is employedfor stripping together with the'stripped vapors being utilized for de-aerating the incoming feed stock, removing the moisture thereof, and the low, boiling fraction containing odor-iferous substances. A still further object is to provide apparatus in which the bottoms from the fract-ionating tower are withdrawn and stripped of vapors at low temperatures. the stri ped vapors being returned without substantial heat loss to the fractionating tower. Other ich 2, October 9. 1939.

objects and advantages the heat exchanger,

is a division of-appiir This 1945, Serial No. 577,246

.will appear as the specification proceeds. The invention is illustrated, in a preferred embodiment, bythe accompanying drawing in which the single figure represents, in a manner one embodiment of apparatus suitable for carrying out the improved process.

The process may be described broadly,-in connection with the apparatus, as follows. The feed stock containing fatty acids enters through pipe in into the heat exchanger, or other suitable form of heater. In. the heat exchanger shown, a heating fluid such as a Dcwtherm' may be passed through the inlet pipe I I and out of the exchanger through the pipe l2. the pipes leading to a suitable-external heating source (not shown) From the stock flows through pipe I3 ,into the stripping about the middle of its top section. As the stock flows downwardly, it meets a rising column of steam and vapors from the steam and vapors aiding in the removal of air and moisture from the feed stock. At the same time, there is removed a small fraction. about five per cent, of low boiling fatty acids and other odoriferous substances. The stripping or fractionatinz tower not only of stripping vapors from the bottoms, but also of fractionating the rising column of .va-' pors.

The steam, air and vapors thus withdrawn pass through the pipe I4 and surface condenser II, the steam passing into the catchail through-pipe l8 and the condensed fatty acid vapors passing I downwardly through pipe ll into the down tank.

The steam in the catchall passes upwardly to a barometric condenser (not shown), by means of which, the pressure on the stripping maintained at about 50 mm. Hg.

'From the down tank, the condensate flows into a pump and about two-thirds of it is returned by the pump to. the top of the stripping tower as reflux. the remaining one-third being removed as product.

The de-aera'ted and dried feed stock then flows by gravity through the pipe l8, which provides a seal l9, into the fractionating tower. Preferably, the top portion of the tower pressure of 2 mm. Hg and the pressure at the base is not greater than 32 mm.

. fractionating tower is heated by a Dowtherm Calandria type of base heater 20.

The vapors from the top of the tower pass of! through pipe ii and are condensed in the surface condenser 22. The major portion of the distillate diagrammatical or fractionating tower at i the bottom of the tower.

described serves the function tower is is maintained at .a

Hz. The bottom of the cooler 25 to a point the stripping tower and passes down from the condenser 22 is returned by the pump 23 thrbugh line 24 tower as reflux. A

to the top of the fractionating smaller portion passes through of recovery.

Bottoms from the tower flow by gravity through the pipe 20, which is formed with a vertical run as shown to trap vapors and to permit a pressure difl'erential thereacross, into'the flash drum or chamber where the vapors, after passing through the entrainment eliminators 21, pass through pipe 2' and are condensed in the surface condenser 28. The condensers 22 and 29 are connected by a manifoldpipe 30 and a vacuum is maintained therein through the use oi vacuum pumps and barometric condensers of well-known structure.

The flash drum is provided with a heating coil 8! connected with the Dowtherm pipes, suitable valves being placed in the lines permitting the coil to be used when desired. In ordinary practice, it is found unnecessary to heat the bottoms within the flash drum. The bottomsfrom the flash drum are withdrawn through pipe 32 and pumped through pipe 33 to a lower portion of the stripping tower. As the bottoms flow downwardly over the trays in the tower, they meet the ascending steam which strips the bottoms. The unvaporized portion of ,the bottoms is withdrawn through pipe 34 and passed through a cooler 35 to a point of recovery.

It will be noticed that the Dowtherm vapor or other suitable heating fluid is circulated through pipes 36 and 31 and through valve controlled pipes leading into the base heater 2!! and the coil 3|, the valves permitting the application of heat-to be accurately controlled in the fractionating tower and in the flash drum.

The distillate which is recovered from the flash drum condenserts passes downwardly through pipe 38 and is then pumped through line 30' and cooler 40 to a point of Specific operation In order to illustrate the operation of the :nethod, a specific example may be given as folows.

Five thousand pounds per hour 01' acidulated cotton seed foots containing from 80 per cent to 85 per cent of free fatty acids (150 the heat exchanger through the pipe l and is brought up to a temperature of 450 F. within the heat exchanger or heater. The stock enters over a series of stripping trays where it is met by a counter current of stripping steam, the pressure on the tower being maintained at approximately 50 mm. Hg.

The vapors pass oil the stripping tower into the surface condenser ii at the rate of 750 pounds per hour where they are condensed, the steam passing to the catchall and finally to the barometric condenser. Five hundred pounds of the condensed low boiling fatty acid is returned to the top of the stripping tower a reflux while 250 pounds is removed as product,

Within the stripping tower, the main portion of the feed stock flows downward over several stripping trays, being thoroughly stripped of noncondensable gases and air, moisture, and low boilingimpurities.

The dried and de-aerated feed stock flows to the main fractionating tower by gravity through line II. A pressure of 2 mm. Hg is maintained at the top of the tower while the pressure at the base is not substantially greater than 32 mm. Hg. The temperature at the base or the tower recovery.

tower and is condensed tower.

per hour of palmitic acid top of the fractionating in the surface condenser 22, 5000 pounds of the condensate being pumped back to the top tray of the i'ractionating tower as reflux and 1000 pound being pumped to storage as finished product. The bottoms, which comprise about 70 to 80 per cent of the incoming stock, are drawn into the flash drum or chamber whiohis maintained at 2 mm. Hg or less, and allowed to vaporize, the latent heat of vaporization being furnished by the sensible heat carried in the stock, no additional heat being required. Twenty-five hundred pounds of the unsaturated acids are removed as vapors in the flash chamber and condensed in the surface condenser 29 from whence it is pumped to storage.

The bottoms from the flash chamber contain considerable quantities of unsaturated acids, the actual percentage being controlled at such an amount as to insure a very pure unsaturated cut; in other words, I avoid getting down too close to the non-volatile matter.

The bottoms (approximately 1500 pounds per hour) are pumped to the top tray oi the bottom section of the stripping tower where they are met with a counter-current of super-heated stripping steam which removes the volatile fatty acids and carries them up to the top section of the tower where they are condensed with the feed stock. The non-volatile matter passes downward over the stripping trays and is removed from the base of the tower, the amount of super-heated steam being regulated so as to give the desired stripping results (approximately 400 pounds per hour). This amount can be varied over fairly wide limits as the pressure in the fractionating tower is from to '70 mm. Hg.

It will be noted that in the new of the feed Six thousand pounds vapor issues from the stock through the stripping-tower. fractionating F.) enters With the new method as described, it i possible to obtain an extremely high vacuum at low costs.. The flash chamber and the fractionating tower can readily be ODeratedat pressures of 1 to 2 mm. Hg without the compression or steam becauseno low boiling materials, water. air and non-condensable gases are present, the steam being eliminated from the fractionating tower and the feed stock being de-aerated and dried in the stripping tower.

Relatively low-temperatures can be employed byvirtue of the removal of the fractions in the stepwise method. The unsaturated fraction is removed by a flash distillation step where no heat is applied during the vaporization stage.

The fatty acid remaining in the bottoms is stripped by means of a high ratio of steam at a point in the system where the steam does not interfere with the high vacuum operation. Eflicient and thorough stripping is accomplished at low temperatures. The stripped fatty acid is returned to the feed stock directly and with no heat loss, the latent heat contained in the acid being utilized for removing the moisture and low boilin material in the feed stock. It will be noted that the unsaturated fraction is heated'only in the fractionating tower. Since the moisture is removed from the feed stock, there is no surgin within the fractionating tower, as wouldotherwise be produced through a variation in the moisture content of the stock.

While in the foregoing description of the process, I have set forth certain steps as desirable, it will be understood that a number of such steps may be omitted or carried on in different seouences without departing from the spirit of my invention.

The phrase "fatty acid-containing stock" .as used herein and in the claims appended, is intended to include pure" fatty acid mixtures and/or stock-containing fatty acids and glycerides, etc.

I wish it to be understood thatI do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

Iclaim:

1. In apparatus of the class set forth, a tube heater through which fresh charging stock may be passed, a stripping andjfractionating tower,

means for. passing the stock from said tube heater into said tower, a second fractionating tower, a

- flash drum, means for returning bottoms from saidflash drum to an-intermediate portion of said first tower, rneans for introducing steam into.

. said flrst towerfcommunicating pipes between said first and second tower permitting stock to flow by pressure difference from said flrst tower into said second tower, and communicating pipes between said second tower and said flash drum permitting stock to flow from said second tower into said flash drum by pressure difference,

2. In apparatus of the class set forth, a tube heater, a first fractionating tower, means for passing stock through said upper portion of said firstfractionating tower, a second tower, means for introducing steam into the lower portion of said flrst tower, means. for producing a pressure below atmospheric in the upper portion of said dirst tower, a flow line permitting flowby pressure difference from a central portion of said first tower into a central portion of said. second tower, means for producing a pressure below atmospheric in the upper portion of said second tower, a flash drum, aflow line causing stock to'flcw by pressure difference from the bottom portion ot said second tower into said flash drum, means for producing a pressure below atmospheric in said flash drum, and means for returning stock from the bottomnof said flash drum to the lower portion of vsaid first tower. '3

3. In apparatus of heater, a first fractionating tower,- meansufor passing stock through said tube heater and into the upper portion of saidflrst tower, in second fractionating tower, means for introducing steam into the lower portion of said flrsttower, a flow line permitting flow by pressure difference of tube heater into the the4'classset forth, a tube 4'. In apparatus of the character set forth for treating fatty acid materials, 7 tower having an upper section containing rectifying apparatus and a lower section containing stripping apparatus, said rectifying apparatus including a series of rectifying zones through which vaporized fatty acid materials mayipass; and ineluding also means for passing liquid fatty acids to said zones as reflux liquid, means for withdrawing a, low boiling fatty acid from said rectifyin section, means for introducing steam into said stripping section, means for withdrawing a bottom material from the lower portion of said stripping section, a second fractionating tower containing a series of rectifying zones, means for introducing reflux liquid vto said zones in said second tower, means forwithdrawing separately a plurality of fatty acid fractions having diflerent boiling points from said second tower, said towers being connected by a closed conduit permittin flow. of liquid from the central portion of said first tower to said second tower and means for maintaining said first tower under a reduced pressure and said second tower under a lower reduced pressure.

- 5. In apparatus of the character-set forth for treating fatty "acid materials, a tube heater through which said fatty acid materials may be passed,- a fractionating tower having an upper section containing rectifyingapparatus "and a lower section containing stripping apparatus,

said rectifying apparatus including a series of fatty acids to'said zones .as reflux liquid, means for passing the heated materials from said tube heater into said tower, means for withdrawing a low boiling fatty acid fraction from said rectifying section, means for withdrawing non-volatile material fromsaid strippingsection, means for introducing steam into said stripping section, a second fractionating tower containing a series of rectifying zones, means for introducing reflux liquid to said zones in said second tower,

. means for withdrawing separately a plurality of fatty acid fractions of different boiling points from said second tower, said towers being connected. by a closed conduit, permitting flow of liquid in a confined stream from said first tower.

to said second tower, and means for maintaining said first tower under a reduced pressure and said second tower under .a lower reduced pressure.

6. .In an apparatus of the character set forth for treating. fatty acid materials, 'a tower conliquid from the central portion of said first tower substantially below the pressure in'the-flrst tower.

taining a series of fractionating zones, means for withdrawing a low boiling fatty acid fractionfrom an upper portion of said series of zones, means for condensing and returning at least a portion of said withdrawn fraction to said upper portionas reflux liquid, a stripping tower for re-v ceiving fatty acidfeed stock, means for introducing steam into. said stripping ,tower to strip the feed stock therein, means for passing a con- 'flned stream of liquid from said stripping tower to said fractionating tower, means for maintainin: said fractionating tower under subatmos-' pheric pressure substantially below the pressure in said stripping tower, means for withdrawing a high boiling fraction containing, non-volatile material from a lower portion of said fractionating tower, and means for passing at least a part of saidwithdrawn fraction to saidmtripping tower.

7. In apparatus of the character set forth for treating fatty'acid materials, a tower containing a series of fractionating zones. means for withdraw- 'a fractionating I from an upper portion of said tower, means for condensing and returning at least a portion of said withdrawn fraction to said tower as reflux liquid, 9, stripping tower for receiving fatty acid feed stock, means for introand said flash drum permitting stock to flow from said second tower into said flash drum.

the upper portion of ducing steam into said stripping tower to strip the feed stock therein, said towers being connected by a closed conduit permitting flow of,

liquid in a confined stream from said stripping tower to said fractionating tower, said conduit being equipped with means for preventing flow of steam with said liquid through the conduit, means'for maintaining said fractionating tower under atmospheric pressure substantially below the pressure in said stripping tower whereby the iractionating tower may be maintained substantially .free of gases and vapors foreign'to said fatty acid materials, means for withdrawing a high boiling fraction containing non-volatile material from a lower portion of said fractionating tower, means for distilling volatile material from said fraction withdrawn, means for maintaining said distilling means under a subatmospher'ic pressure lower than the pressure inthe lower portion of said fractionating tower, and means for passing non-volatile matter from said distilling means to said stripping tower.

8. In apparatus of the character set forth for treating fatty acid materials, a tower containing a series of fractionating zones, means for withdrawing a low boiling fatty acid fraction from an upper portion of said tower, means for condensing and returning at least a portion of said withdrawn fraction to the upper portion of said tower as reflux liquid, 8, stripping tower, means for introducing steam into said stripping tower, means for maintaining said fractionating tower under subatmospheric pressure substantially lower than the pressure in said stripping tower, said fractionating tower being substantially free of gases foreign to said fatty acid materials, means for withdrawing a high boiling fraction containing non-volatile material from a lower portion of said fractionating tower, means for passing at least a part of said withdrawn high boiling fraction to said stripping tower, and conduit means 10. In apparatus for treating fatty acid materials, ,a first fractionating tower, means for passing fatty acid material stools into said fractionating tower, means for introducing steam into said tower, means for producing a pressure below atmospheric in the upper portion of said tower, a second fractionating tower, a flow line permitting flow of liquid from said first tower to said second tower, means for producing a subatmospheric pressure in the upper portion of the second tower lower than the pressure in the upper portion of the first tower, a fiash drum, a flow line for permitting liquid to flow from the lower portion of said second tower into said flash drum, means for producing a subatmospheric pressure in said flash drum below the pressure in the lower portion of said second tower, and means for returning stock from the bottom of said flash drum to the lower portion of said first tower.

11. In apparatus for the separation or a mixture containing fatty acids of different boiling points, a fractionating tower equipped with means for supporting a series of spaced pools of fatty acid within said tower, means for introducing fatty acid stock into said tower, an outlet in said tower for withdrawing lower boiling vaporized fatty acid from above the upper 0! said poolsupporting means, means for maintaining in said tower about the upper of said pool-supporting means a high vacuum which extends to a lesser degree about the lower of said pool-supsaid tower, a flash drum providing porting means, means forintroducing steam into a distillation chamber, means including a, conduit for passing liquid higher boiling fatty acid from the lower of said pool-supporting means to said flash drum,

connecting said stripping tower to said fractionating tower whereby liquid acids stripped from said non-volatile material may pass again to said fractionating tower, said conduit means being equipped with a trap for preventing flow of steam with said liquid acids through said conduit means.

9. In apparatus for treating fatty acid materials, a stripping and fractionating tower, means for passing the fatty acid material stock into said tower, at second iractionating tower, a flash drum, means for returning stock from said flash drum to an intermediate portion of said first tower, means for introducing steam into said first tower, communicating conduits between said first and second towers permitting said stock to flow from said first tower into said second tower, and communicating conduits between said second tower means for maintaining a, high vacuum in said distillation chamber which vacuum is higher than the vacuum about the lower of said pool-supporting means in said tower, an outlet for withdrawing vaporized higher boiling fatty acid from said drum, and an outlet for withdrawing unvaporized residue from said drum.

RALPH H. POI'TS.

REFERENCES CITED The following references are of record in the file of this patent;

UNITED STATES PATENTS Number Name Date 1,559,218 Barbet Oct. 17, 1925 1,698,798 Legendre Jan. 15, 1929 1,806,571 Howard at al May 19, 1931 1,946,020 Gorhan Feb, 6, 1934 1,979,185 Barbet Oct. 30, 1934 2,107,156 Kubn et al Feb. 1, 1938 2,125,325 Youker Aug. 2, 1938 2,132,137 Watson Oct. 4, 1938 2,147,306 McCullogh Feb. 14, 1939 2,224,984 Potts et a1. Dec. 17, 1940 2,240,752 Bogart et al. May 6, 1941 2,322,056 Potts June 15, 1943 

